Last week, Arizona Representative Paul Gosar posted on Twitter and Instagram a photoshopped animated cartoon in which he assassinates Representative Alexandria Ocasio-Cortez and attacks President Joe Biden.

Gosar says it “symbolizes the battle for the soul of America” when Congress takes up the president’s economic package, which he said includes immigration provisions he opposes.

Gosar represents Arizona’s 4th congressional district. Until 2012, a dear friend of mine, Gabrielle Giffords, represented Arizona’s 8th congressional district.

I got to know Gabby shortly before she entered politics as a member of the Arizona state house of representatives in 2001. She then became the youngest woman ever elected to the Arizona senate and then, in 2006, the third woman in history to be elected to represent Arizona in the US House of Representatives.

On 8 January 2011, during a public gathering outside a Safeway grocery store in Casa Adobes, Arizona, Gabby was shot in the head by a man firing a 9mm pistol with a 33-round magazine.

He hit 19 people and killed six, among them federal judge John Roll and a nine-year-old girl, Christina-Taylor Green. The shooter, Jared Lee Loughner, was detained by bystanders until he was taken into police custody. Eventually, after facing more than 50 federal criminal charges, Loughner pleaded guilty to 19 of them to avoid a death sentence.

Gabby was evacuated to the University Medical Center of Tucson in critical condition. By the time I was able to see her the following week, she could say a few words. But even now, a decade later – after the most intense and courageous personal effort at rehabilitation I have ever witnessed – she continues to struggle with language and has lost half her vision in both eyes. Gabby resigned from Congress in 2012.

Why did Loughner try to assassinate her? No one will ever know for sure. Authorities found in his safe an envelope that bore the handwritten words “Giffords”, “My assassination” and “I planned ahead.” By all accounts, including his own, he was growing increasingly delusional. He had amplified on his social media accounts several extremist rightwing tropes.

In March 2010, 10 months before the shooting, former vice-presidential candidate Sarah Palin had posted a map of 20 congressional districts she and John McCain won in 2008 but whose representatives in Congress had voted in favor of the Affordable Care Act. The map marked each district with a set of crosshairs. Palin promoted the map by tweeting “Don’t Retreat, Instead – RELOAD.” One of those crosshairs targeted Gabby.

Although no direct connection was ever established between Palin’s map and Gabby’s shooting, surely Palin’s violent rhetoric contributed to a climate of political violence in America in which a delusional man would mark Gabby for assassination. Gabby herself had expressed concern about Palin’s map.

Just as surely, Palin’s inflammatory post was a step toward increasingly violent political rhetoric on the way to Donald Trump and the insurrection of 6 January.

Last Friday a group of House Democrats introduced a resolution to censure Gosar for posting his video. The motion was introduced by Representative Jackie Speier, co-chair of the Democratic women’s caucus, and nine other lawmakers. “For that Member to post such a video on his official Instagram account and use his official congressional resources in the House of Representatives to further violence against elected officials goes beyond the pale,” the group said. “As the events of January 6th have shown, such vicious and vulgar messaging can and does foment actual violence.”

The House Republican leader, Kevin McCarthy, has so far been silent on Gosar’s video. The group of House Democrats who introduced the resolution condemned McCarthy’s silence, calling it “tacit approval and just as dangerous”.

America is experiencing increasingly virulent politics and violent political threats. The New York Times reports that at a conservative rally in western Idaho last month, a young man stepped up to a microphone to ask when he could start killing Democrats. “When do we get to use the guns?” he said, as the audience applauded. “How many elections are they going to steal before we kill these people?” The local state representative, a Republican, later called it a “fair” question.

According to the Times, violent threats against lawmakers are on track to double this year. Republicans who break party ranks and defy Trump have come to expect death threats – often incited by their own colleagues, who have denounced them as traitors.

Unless those at the highest levels of government who foment or encourage violence – or who remain conspicuously silent as others do – are held accountable, no one in political life will be safe.

Censure is not enough for Gosar. He should be expelled from the House.

• Robert Reich, a former US secretary of labor, is professor of public policy at the University of California at Berkeley and the author of Saving Capitalism: For the Many, Not the Few and The Common Good. His new book, The System: Who Rigged It, How We Fix It, is out now. He is a Guardian US columnist. His newsletter is at robertreich.substack.com